BIOL 155 Lecture Notes - Lecture 10: Neuromuscular Junction, Motor Neuron, Motor Unit
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Ubc biol 155 lecture 9 notes muscular system. Each muscle fibre contracts in an all or none fashion. Muscles are composed of a large number of cells organized into motor units. Each muscle is innervated by at least 1 motor neuron; hundreds of motor axons; each axon forms a neuromuscular junction with a single muscle fibre. Motor neuron fires; simultaneous contraction of all the muscle fibers in the motor unit. In muscles with many motor units, the individual muscle fibres associated with each motor neuron are not clustered together, but spread through out the muscle; therefore, if only one motor unit is stimulated the entire muscle contracts very weakly. Fine motor control (eyes, finger); small motor units. Large, weight bearing muscles needing imprecise control; larger motor units: graded muscle responses, definition: variations in the degree of muscle contraction required for proper control of muscle movement. Multiple motor unit summation or recruitment (strength of stimulation)
